In printheads with a plurality of print elements arranged movable in relation to each other it is already known to have a moving mechanism with magnetic field-responsive forces for moving selectable print elements to print and rest positions. In such cases it is also known to have in the moving mechanism a plurality of electromagnetic means with changeable current for achieving magnetic field changes, and thereby changes in the magnetic field-responsive forces. Such printheads are known from such as U.S. Pat. Nos. 4,233,894, 4,393,771, 4,438,692, 4,503,758 and 4,509,421.
Mechanical springs, permanent magnets and electromagnets are used in moving mechanisms in printheads of the kind given above for moving the print elements individually and in groups to print and inactive positions. For example, the U.S. Pat. No. 4,584,937 teaches the use of a common permanent magnet for several print elements, with individual electromagnetic cores of ferromagnetic material and to have individual electromagnetic windings for each print element. Here, the permanent magnet is adapted such that it is included in a magnetic circuit for each of the print element. A mechanism spring is associated with each print element, and adapted such that its spring bias strives to move the element towards a given print position when the element is in a given inactive position. However, in the absence of current in one electromagnet means the magnet fieldresponsive forces originating from the permanent magnet in the magnet circuit are sufficiently strong to overcome the spring bias, and to keep the print element in its inactive position. For selectively moving print elements individually or in groups to their print positions, a current of suitable size and direction is supplied to an electromagnet winding in the electromagnet means which is/are associated with the selectable print element(s) which is/are to be moved. The respective current then weakens the magnetic field in the magnetic circuit in the respective print element so that the magnetic field-responsive forces become weaker than the mechanical spring forces, and the respective print element can be moved to its print position by the spring bias.